An image encryption scheme based on hybridizing digital chaos and finite state machine

Abstract

Image encryption protects visual information by transforming images into an incomprehensible form. Chaotic systems are used to design image ciphers due to properties such as ergodicity and initial condition sensitivity. A chaos-based cipher derives its security strength from its underlying digital chaotic map, thus a more complex map leads to higher security. This paper introduces an enhancement to a tent map’s chaotic properties by hybridizing it with a deterministic finite state machine. We denote the resulting digital one-dimensional chaotic system as TM-DFSM. Chaotic analyses indicate that the new chaotic system has higher nonlinearity, sensitivity to initial condition, and larger chaotic parameter range than other recently proposed one-dimensional chaotic systems. We then propose a new image encryption scheme based on TM-DFSM, capable of performing both confusion and diffusion operations in one pass while also having a flexible key space. The encryption operations are designed to achieve maximal confusion and diffusion properties. Changing a single bit of the plainimage or secret key will result in an entirely different cipherimage. The proposed cipher has been analyzed using histogram analysis, contrast analysis, local Shannon entropy, resistance against differential cryptanalysis, and key security. Performance comparison with other recent schemes also depicts the proposed cipher’s superiority.